The base was one of the top Soviet military secrets that was revealed by U.S. reconnaissance only in 1978.

Whether or not Soviet nuclear secrets leak into the third world, the proliferation challenges there are manifold.

For decades the region around Izhevsk, known as Udmurtiya - closed, snowbound and forgotten - was simply another Soviet secret that nobody wanted to know.

It's not as if the 300th anniversary of the city's founding were a Soviet secret that had only just been declassified.

Although the Soviet authorities generally cooperated in providing data, they refused to disclose total gold reserves, a long-held Soviet secret.

All Haber had told him was that he'd been apprehended in Moscow and accused of receiving Soviet military secrets during an exchange visit.

By many accounts, the agency had broken through by the early 1980's to gain access to critical Soviet military secrets.

It was his status in this section which allowed him to learn many Soviet secrets by reading the top secret ciphers.

A submarine driver brings Soviet nuclear secrets to the United States.

His success in obtaining Soviet secrets allegedly led the Soviets to send a false defector on an ultimately unsuccessful assassination mission.